To determine the prevalence of frequently occurring neurologic disorders in a biracial population, a survey of households and chronic care institutions was carried out for all residents of Copiah County, MS. Along with a complete census, interviews were held using extensive questions about diagnoses, signs, and symptoms of neurologic disorders. Over 97% of eligible households participated, comprising 23,842 persons (49% black, 50% white, 1% other). Persons with responses suggesting one or more of these disorders were examined by a neurologist who used defined diagnostic criteria. Age-adjusted prevalence ratios for cerebral palsy, epilepsy, stroke, and severe dementia were somewhat higher in blacks than in whites, while the age-adjusted prevalence ratio for essential tremor was slightly higher in whites. For Parkinson's disease, there was no difference in age- adjusted prevalence ratios between the races. With respect to particular disabilities in persons with the disorders mentioned above, it was found that proportionately more institutionalized men than institutionalized women were functionally disabled.